One known method of shaping honeycomb core includes placing the core on a series of horizontal support rods and sliding the combination into an oven. The core is heated to its forming temperature, i.e., the particular temperature at which the core becomes shape-able. Once the core is properly heated, the support rods and core are removed from the oven and the rods are retracted laterally to either side. This causes the core to fall loosely onto a lower die. A worker then correctly aligns the core relative to the die. The heated core is pressed for a period of time between the lower die and an upper die that is shaped in the reverse-image of the lower die (i.e., male/female die pair). The upper and lower dies continue to hold the core until it cools in the ambient air to a set temperature. Once set, the dies recede, and the shaping process is complete.
There are a number of disadvantages associated with the above method. A first disadvantage is that extra energy is required to heat the core in order to compensate for heat lost during transfer of the core from the rods to the lower die and heat lost to the dies during pressing. The core must be heated to a particular temperature in order to bring it to a malleable state. Even if the initial temperature of the core is correctly adjusted, the forming temperature is adversely affected because the dies continue to absorb heat from the core during pressing. This reduces the amount of time available for pressing the core at the required forming temperature. A second disadvantage is that after the core is pressed at its proper forming temperature, the core must be allowed to cool to a particular temperature while still being held at its new shape. If the core is released prior to reaching this set temperature, it will tend to return (i.e., spring back) toward its original shape. This cool down period is longer than desired when using the above method due to the slow rate of heat dissipation from the upper and lower dies.
Many of these disadvantages are addressed in the method and apparatus described in U.S. Pat. No. 5,780,074. In particular, the '074 patent describes an embodiment for forming a settable material in which the material is placed on a flexible support, transferred to and from an adjacent oven, and then pressed between the flexible support and an upper male die. After pressing, the flexible support and upper die continue to hold the core until it has cooled in the ambient air to its set temperature. Once cooled, the upper die recedes. Shaping of the material is complete. The '074 patent thus reduces the problems associated with core heat loss prior to and during forming. The '074 patent also reduces the cool down time required for setting the material, since the flexible support dissipates heat much faster than a (typically metal) lower die.
If has been found in using the above '074 process, however, that the production time required to manufacture a large number of shaped panels is unacceptably high. This is partly due to the time required to ambiently cool the material to its set temperature while being held in its new shape. The '074 addressed this need in part, by providing an embodiment in which the lower, female die is eliminated. This allows heat to dissipate more quickly from the core, thus causing it to reach its set temperature faster. The upper, male die, however, yet remains as an impediment to the dissipation of heat from the core. Therefore, a continued need for a shaping method and apparatus exists that provides faster, more efficient technique for bringing the core to its set temperature during the cool down period. The present invention is directed to fulfilling this need.